function mouseThrow() {
    let canvas = document.getElementById("_canvas");
    let ctx = canvas.getContext("2d");
    let engine = new Engine(ctx);
    let layer = new Layer(ctx); 
    
    layer.create = function () {
        let axis = new CoordinateObject();
        layer.addObject(axis);

        let polygon = new PolygonObject();
        polygon.radius = 80;
        polygon.x = 200;
        polygon.y = 200;
        polygon.degeCount = 3;
        polygon.addComponent(new GameComponent.AxisDottedLine());
        polygon.addComponent(new GameComponent.MouseThrow());
        polygon.addComponent(new GameComponent.Tip('三边形'));
        polygon.addComponent(new GameComponent.SpeedTip());
        // polygon.addComponent(new GameComponent.MoveToClick());
        polygon.update = function () {
            if (this.x <= 0 || this.x >= canvas.width
                || this.y <= 0 || this.y >= canvas.height) {
                this.moving = false;
            }
        }
        layer.addObject(polygon);
    }
    engine.addLayer(layer);
    engine.run();
    return engine;
}